Google has launched a tool that allows users to tailor their searches to the websites and blogs they are most interested in.

Google Custom Search Engine can be focused on any content the user likes, how this should be prioritised, whether others can contribute to their index, and what the search results page will look like.

People can even create search engines pointing their friends to sites about their favorite pop stars and place them on their personal homepages.

A number of sites have already used the tool to create their own custom search engines. For example, Real Climate, a site that offers expert opinion on the science of climate change is using it to point visitors to other sites it says provide reliable scientific information.

These subsets of pages on the internet have been validated by Real Climate and include government labs, research institutes as well as Real Climate research.

The website owners said: "As we get used to this service, we will be adding sites and pages that we feel are up to the mark. Suggestions for sites we might not yet have found or have overlooked, will of course be welcome."

Users can also specify whether or not the tool can be used to generate some income by using the Google Adsense program to generate advertisements from search terms.

Advertisers pay Google every time someone clicks on these adverts and, in return, people who incorporate Adsense on their custom search engines will also receive a portion of the amount paid to Google.

"We want to make it easy for anyone to create a search engine about all their favorite topics, without needing a PhD," said Marissa Mayer, Google's vice -president of search products and user experience.

"Everyone can harness the power of Google technology to create a personalised search experience that reflects specific knowledge and interests."